A IN - out/out singleside
B https://www.printables.com/cs/model/285433-brioplaytive-racing-track-2-way1-way-reduction singleside
C IN - in/in singleside
D OUT - out/out singleside
E IN - in/out doubleside
F OUT - in/out doubleside
The author hasn't provided the model origin yet.